Types of RFC communication

This article answers the following queries:

• What are the different RFC communication types in SAP?
• What is the difference between Synchronous and Asynchronous RFC types?
• What is the RFC communication type in which all requests are processed in order they are received?
• What is the difference between Transactional RFC and Queued RFC?
• What is/are the RFC types in which remote system is not required to be     available at the moment the RFC client program start the call?
• In what scenarios, Queued RFC type can be used?

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There are mainly 4 types of RFC communication in SAP. They are

• Synchronous RFC
• Asynchronous RFC
• Transactional RFC
• Queued RFC

Synchronous RFC (sRFC) :  In this type of RFC communication, the calling program waits until the requested processing step on the remote system has ended and then continues to work locally.

In other words, both the systems involved must be available at the time the call is made.

Asynchronous RFC (aRFC) : In this type of RFC communication, the calling program gives the request to the remote system and immediately continues to work locally. The requested processing step is executed on the remote system in isolation.

If the remote system cannot be reached at the time of the call, the asynchronous calls of the RFC client are lost

Transactional RFC (tRFC) : This type of RFC communication is similar to asynchronous RFC but by allocating a transaction id(TID)  it guarantees  that if a request is sent several times because of network problems  it is processed only once. Unlike asynchronous RFC,  in Transactional RFC the remote system does not have to be available at the moment the RFC client program start the call. The data is held in the source system until the target system is available.

The report program RSARFCSE is called in the background at regular intervals and tries to place the unsuccessful requests, identified by their transaction id again.

Queued RFC (qRFC) : This RFC communication is an extension to the transactional RFC. In this method, all the requests are queued up(inbound queue and outbound queue) and are processed in a sequence only if it is certain that all preceding calls are processed correctly. This method guarantees that all the requests are processed in the sequence in which they are received.

This type of RFCs will be used in SCM (APO) systems for CIF queues etc where requests have to be processed in an order.